What is a no follow link?
To answer this question first we must provide a quick background on how a regular link operates within the field of search engine optimisation (SEO). Regular links, called natural links, connect sites through the use of a text or image hyperlink.
Simplified, search engines measure these inbound links and use them as a metric to calculate a websites authority on a topic. The more reputable the site that links to you, the more link authority is passed along to your site. This can help to improve your ranking on a search engine results page.
You could consider a link as a vote of recommendation from the Internet. Generally, the more votes the better but if your vote is from a very important person it will carry a lot more weight. ‘Link juice’ is a term often used to describe the SEO benefits passed to a site through links.
Now we understand how a natural link affects SEO we can classify a no follow link as a link that connects a site without passing on any SEO benefits. The link will still operate as a hyperlink connecting to a site however ‘link juice’ will not flow to the site.
The no follow attribute can appear in the page-level meta tag and instruct search engines not to index any outbound links on the page:
<meta name=”robots” content=”nofollow” />
Alternatively, the no follow attribute can be applied to specific links within the page:
<a href=”signin.php” rel=”nofollow”>sign in</a>
Why do we need no follow links?
During the early days of SEO many people would attempt to create as many inbound links to their site as possible to increase search rankings. This resulted in blogs and forums being saturated with spam from self-promotional links. Of course, this ruined the ability of sites to build an online community with thoughtful discussion.
Consequently, the no follow attribute is automatically applied to all user submitted links in WordPress and on Wikipedia. The no follow link has not stopped comment spamming completely but it has certainly saved the internet from a lot.
The no follow attribute also serves a function for SEO experts to avoid being penalised by search engines for duplicate content issues. Duplicate content is very similar content that appears on the internet at more than one URL. It confuses search engines and is detrimental to a sites search rankings. For instance if there was a separate page for a range of colours of a single product then each page could be seen as duplicate content. However this issue can be sidestepped by using no follow links to the pages with duplicate content. This informs search engines that they should not index the content on the page and stops the confusion.
Overall, no follow links do not pass on SEO benefits the same way a natural link does but they do serve a valuable purpose.